Below I have put together the SEO modules I am currently using in my projects. Drupal 8 is by far the best release to date, packed full of features and SEO implementations out of the box. Saying that there is always times when contributed modules are a life saver! This is mainly a list for me to refer to but it may help you too :) This is posted August 2018.
As always, when installing new modules it's best to use composer. I personally use PuTTY to connect to the command line. By installing modules this way (composer require drupal/drupal_module_name) it will automatically install any required modules and any 3rd party libraries at the same time.